#include<stdio.h>

int main()
{
	int n;
	scanf("%d",&n);
	double sum=1;
	if(n==0||n==1) 
	{	
		printf("%lf\n",sum);
		return 0;
	}
	while(n!=0)
	{
		sum*=n;
		n--;
	}
	printf("%lf\n",sum);
	
	
	return 0;
}